This invention relates to freeze dryers in general and, in particular, to manifold-type freeze dryers.
Commercially available manifold-type freeze dryers enjoy heavy use in laboratory and research applications. These freeze dryers normally include a refrigeration systen having a refrigeration compressor, a condenser, a restrictor and an evaporator (freeze-drying condenser), and a vacuum system mounted in a base supporting a manifold tube having a series of ports and associated valves for receiving specimen containers. The manifold tube is in communication with the freeze drying condenser which is usually an enclosed metal container or vessel cooled by the refrigeration system. A vacuum is applied through the manifold tubing and the condenser by the vacuum system to sublimate the water vapor from the specimen through the entire manifold tube into the condenser.
These prior devices, because of their construction, were difficult to clean and disinfect. In addition, the location of the condenser apart from the manifold on which the specimen containers were mounted, increases the volume which the vacuum system must draw down and requires the water vapor to travel a long and tortuous path between the product and the condenser. These factors slow both cooling time and system recovery as further product containers are added to the manifold. Presently available freeze dryers of this type also have limited freeze drying capacity because of the inability of the condenser to handle heavy loads and maintain low temperatures without increasing the size and cost of the refrigeration system. Finally, the refrigeration and vacuum components in prior systems were often inaccessible and therefore, difficult to service and maintain.